19-2030; Rev 0; 4/01
IT
TION K
VALUA
E
BLE
AVAILA
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
General Description
The MAX1864/MAX1865 power-supply controllers are
designed to address cost-conscious applications such
as cable modem Consumer Premise Equipment (CPE),
xDSL CPE, and set-top boxes. Operating off a low-cost,
unregulated DC supply (such as a wall adapter output),
the MAX1864 generates three positive outputs, and the
MAX1865 generates four positive outputs and one neg-
ative output to provide a cost-effective system power
supply.
The MAX1864 includes a current-mode synchronous
step-down controller and two positive regulator gain
blocks. The MAX1865 has one additional positive gain
block and one negative regulator gain block. The main
synchronous step-down controller generates a
high-current output that is preset to 3.3V or adjustable
from 1.236V to 0.8
✕
V
IN
with an external resistive-
divider. The 100kHz/200kHz operating frequency
allows the use of low-cost aluminum-electrolytic capaci-
tors and low-cost power magnetics. Additionally, the
MAX1864/MAX1865 step-down controllers sense the
voltage across the low-side MOSFET’s on-resistance to
efficiently provide the current-limit signal, eliminating
the need for costly current-sense resistors.
The MAX1864/MAX1865 generate additional supply
rails at low cost. The positive regulator gain blocks use
an external PNP pass transistor to generate low-voltage
rails directly from the main step-down converter (such
as 2.5V or 1.8V from the main 3.3V output) or higher
voltages using coupled windings from the step-down
converter (such as 5V, 12V, or 15V). The MAX1865’s
negative gain block uses an external NPN pass transis-
tor in conjunction with a coupled winding to generate
-5V, -12V, or -15V.
All output voltages are externally adjustable, providing
maximum flexibility. Additionally, the MAX1864/
MAX1865 feature soft-start for the step-down converter
and all the positive linear regulators, and have a power-
good output that monitors all of the output voltages.
♦
4.5V to 28V Input Voltage Range
♦
Master DC-DC Step-Down Converter
Preset 3.3V or Adjustable (1.236V to 0.8
✕
V
IN
)
Output Voltage
Fixed-Frequency (100kHz/200kHz) PWM
Controller
No Current-Sense Resistor
Adjustable Current Limit
95% Efficient
♦
Two (MAX1864)/Four (MAX1865) Analog
Gain Blocks
Positive Analog Blocks Drive Low-Cost PNP
Pass Transistors to Build Positive Linear
Regulators
Negative Analog Block (MAX1865) Drives a
Low-Cost NPN Pass Transistor to Build a
Negative Linear Regulator
♦
Power-Good Indicator
♦
Soft-Start Ramp for All Positive Regulators
Features
MAX1864/MAX1865
Ordering Information
PART
MAX1864TEEE
MAX1864UEEE
MAX1865TEEP
MAX1865UEEP
TEMP.
RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
16 QSOP
16 QSOP
20 QSOP
20 QSOP
f
OSC
(kHz)
200
100
200
100
Pin Configurations
TOP VIEW
POK 1
16 IN
15 VL
14 BST
Applications
xDSL, Cable, and ISDN Modems
Set-Top Boxes
Wireless Local Loop
COMP 2
OUT 3
FB 4
B2 5
FB2 6
B3 7
FB3 8
MAX1864
13 DH
12 LX
11 DL
10 GND
9
ILIM
16 QSOP
Pin Configurations continued at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
MAX1864/MAX1865
ABSOLUTE MAXIMUM RATINGS
IN, B2, B3, B4 to GND............................................-0.3V to +30V
B5 to OUT...............................................................-20V to +0.3V
VL, POK, FB, FB2, FB3, FB4, FB5 to GND ...............-0.3V to +6V
LX to BST..................................................................-6V to +0.3V
BST to GND ............................................................-0.3V to +36V
DH to LX ....................................................-0.3V to (V
BST
+ 0.3V)
DL, OUT, COMP, ILIM to GND......................-0.3V to (V
L
+ 0.3V)
VL Output Current ...............................................................50mA
VL Short Circuit to GND...................................................≤100ms
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........666mW
20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
IN
= 12V, ILIM = FB = GND, V
BST
- V
LX
= 5V,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
GENERAL
Operating Input Voltage Range
(Note 1)
Quiescent Supply Current
VL REGULATOR
Output Voltage
Power-Supply Rejection
Undervoltage Lockout Trip Level
Minimum Bypass Capacitance
DC-DC CONTROLLER
Output Voltage (Preset Mode)
Typical Output Voltage Range
(Adjustable Mode) (Note 2)
FB Set Voltage
(Adjustable Mode)
FB Dual Mode™ Threshold
FB Input Leakage Current
FB to COMP Transconductance
Current-Sense Amplifier Voltage
Gain
Current-Limit Threshold
(Internal Mode)
Current-Limit Threshold
(External Mode)
I
FB
g
m
A
LIM
V
VALLEY
V
VALLEY
V
FB
= 1.5V
FB = COMP, I
COMP
=
±5µA
V
IN
- V
LX
= 250mV
V
ILIM
= 5.0V
V
ILIM
= 2.5V
70
4.46
190
440
V
OUT
V
OUT
V
SET
FB = COMP
FB = GND
3.272
1.236
1.221
50
1.236
100
0.01
100
4.9
250
530
3.314
3.355
0.8 x V
IN
1.252
150
100
140
5.44
310
620
V
V
V
mV
nA
µS
V/V
mV
mV
VL
PSRR
V
UVLO
C
BYP(MIN)
6V < V
IN
< 28V, 0.1mA < I
LOAD
< 20mA
V
IN
= 6V to 28V
VL rising, 3% hysteresis (typ)
10mΩ < ESR < 500mΩ
3.2
3.5
1
4.75
5.00
5.25
3
3.8
V
%
V
µF
V
IN
V
FB
= 0, V
OUT
= 4V,
V
FB2
= V
FB3
= V
FB4
= 1.5V,
V
FB5
= -0.1V
MAX1864
MAX1865
4.5
1.0
1.4
28
2
mA
3
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
I
IN
Dual Mode is a trademark of Maxim Integrated Products, Inc.
2
_______________________________________________________________________________________
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V, ILIM = FB = GND, V
BST
- V
LX
= 5V,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
Switching Frequency
Maximum Duty Cycle
Soft-Start Period
Soft-Start Steps
DH Output Low Voltage
DH Output High Voltage
DL Output Low Voltage
DL Output High Voltage
DH, DL On-Resistance
Output Drive Current
LX, BST Leakage Current
POSITIVE ANALOG GAIN BLOCKS
FB2, FB3, FB4 Regulation
Voltage
FB2, FB3, FB4 to B_
Transconductance
Feedback Input Leakage
Current
Driver Sink Current
NEGATIVE ANALOG GAIN BLOCK
FB5 Regulation Voltage
FB5 to B5 Transconductance
Feedback Input Leakage
Current
Driver Source Current
POWER GOOD (POK)
OUT Trip Level (Preset Mode)
FB Trip Level (Adjustable Mode)
FB2, FB3, FB4 Trip Level
FB5 Trip Level
POK Output Low Level
POK Output High Leakage
THERMAL PROTECTION (Note 3)
Thermal Shutdown
Thermal Shutdown Hysteresis
Rising temperature
160
15
°C
°C
FB = GND, falling edge, 1% hysteresis (typ)
Falling edge, 1% hysteresis (typ)
Falling edge, 1% hysteresis (typ)
Rising edge, 35mV hysteresis (typ)
I
SINK
= 1mA
V
POK
= 5V
2.88
1.070
1.070
368
3
1.114
1.114
500
3.12
1.159
1.159
632
0.4
1
V
V
V
mV
V
µA
ΔV
FB5
I
FB5
I
B5
V
B5
= V
OUT
- 2V, V
OUT
= 3.5V, I
B5
= 1mA
(source)
V
B5
= 0, I
B5
= 0.5mA to 5mA (source)
V
FB5
= -100mV
V
FB5
= 200mV, V
B5
= V
OUT
- 2.0V, V
OUT
=
3.5V
10
-20
-5
-13
0.01
25
+10
-20
100
mV
mV
nA
mA
ΔV
FB
_
I
FB
_
I
B
_
V
B2
= V
B3
= V
B4
= 5V,
I
B2
= I
B3
= I
B4
= 1mA (sink)
V
B2
= V
B3
= V
B4
= 5V, I
B2
= I
B3
= I
B4
=
0.5mA to 5mA (sink)
V
FB2
= V
FB3
= V
FB4
= 1.5V
V
FB2
= V
FB3
=
V
FB4
= 1.188V
V
B2
= V
B3
= V
B4
= 2.5V
V
B2
= V
B3
= V
B4
= 4.0V
10
1.226
1.240
-1
0.01
23
26
1.257
-1.75
100
V
%
nA
mA
Sourcing or sinking, V
DH
or V
DL
= VL/2
V
BST
= V
LX
= V
IN
= 28V, V
FB
= 1.5V
I
SINK
= 10mA, measured from DH to LX
I
SOURCE
= 10mA, measured from BST to DH
I
SINK
= 10mA, measured from DL to GND
I
SOURCE
= 10mA, measured from DL to GND
V
L
- 0.1
3
0.5
0.03
20
10
0.1
0.1
SYMBOL
f
OSC
D
MAX
t
SOFT
MAX186_T
MAX186_U
CONDITIONS
MIN
160
80
77
TYP
200
100
82
1024
V
REF
/64
0.1
MAX
240
120
90
UNITS
kHz
%
1/f
OSC
V
V
V
V
V
Ω
A
µA
MAX1864/MAX1865
_______________________________________________________________________________________
3
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
MAX1864/MAX1865
ELECTRICAL CHARACTERISTICS
(V
IN
= 12V, ILIM = FB = GND, V
BST
- V
LX
= 5V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 4)
PARAMETER
GENERAL
Operating Input Voltage Range
(Note 1)
Quiescent Supply Current
VL REGULATOR
Output Voltage
Power-Supply Rejection
Undervoltage Lockout Trip Level
DC-DC CONTROLLER
Output Voltage (Preset Mode)
Feedback Set Voltage
(Adjustable Mode)
Current-Sense Amplifier Voltage
Gain
Current-Limit Threshold
(Internal Mode)
Current-Limit Threshold
(External Mode)
Switching Frequency
Maximum Duty Cycle
POSITIVE ANALOG GAIN BLOCKS
FB2, FB3, FB4 Regulation
Voltage
FB2, FB3, FB4 to B_
Transconductance
NEGATIVE ANALOG GAIN BLOCK
FB5 Regulation Voltage
FB5 to B5 Transconductance
ΔV
FB5
V
B5
= V
OUT
- 2V, V
OUT
= 3.5V, I
B5
= 1mA
(source)
V
B5
= 0, I
B5
= 0.5mA to 5mA (source)
-25
+10
-30
mV
mV
ΔV
FB
_
V
B2
= V
B3
= V
B4
= 5V, I
B2
= I
B3
= I
B4
=
1mA (sink)
V
B2
= V
B3
= V
B4
= 5V, I
B2
= I
B3
= I
B4
=
0.5mA to 5mA (sink)
1.215
1.265
-2.25
V
%
V
OUT
V
SET
A
LIM
V
VALLEY
V
VALLEY
f
OSC
D
MAX
FB = GND
FB = COMP
V
IN
- V
LX
= 250mV
V
ILIM
= 5V
V
ILIM
= 2.5V
MAX186_T
MAX186_U
3.247
1.211
4.12
150
400
160
80
74
3.380
1.261
5.68
350
660
240
120
90
V
V
V/V
mV
mV
kHz
%
VL
PSRR
V
UVLO
6V < V
IN
< 28V, 0.1mA < I
LOAD
<20mA
V
IN
= 6V to 28V
VL rising, 3% hysteresis (typ)
3
4.75
5.25
3
4
V
%
V
V
IN
V
FB
= 0, V
OUT
= 4V, V
FB2
= V
FB3
= V
FB4
= 1.5V,
V
FB5
= -0.1V
MAX1864
MAX1865
4.5
28
2
mA
3
V
SYMBOL
CONDITIONS
MIN
MAX
UNITS
I
IN
4
_______________________________________________________________________________________
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V, ILIM = FB = GND, V
BST
- V
LX
= 5V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 4)
PARAMETER
POWER GOOD (POK)
OUT Trip Level (Preset Mode)
FB Trip Level
(Adjustable Mode)
FB2, FB3, FB4 Trip Level
FB5 Trip Level
FB = GND, falling edge, 1% hysteresis (typ)
Falling edge, 1% hysteresis (typ)
Falling edge, 1% hysteresis (typ)
Rising edge, 35mV hysteresis (typ)
2.85
1.058
1.058
325
3.15
1.17
1.17
675
V
V
V
mV
SYMBOL
CONDITIONS
MIN
MAX
UNITS
MAX1864/MAX1865
Note 1:
Note 2:
Note 3:
Note 4:
Connect VL to IN for operation with V
IN
< 5V.
See
Output Voltage Selection
section.
The internal 5V linear regulator (VL) powers the thermal shutdown block. Shorting VL to GND disables thermal shutdown.
Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, V
IN
= 12V, V
OUT
= 3.3V, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(PRESET MODE)
MAX1864/65 toc01
OUTPUT VOLTAGE vs. LOAD CURRENT
(PRESET MODE)
MAX1864/65 toc02
EFFICIENCY vs. LOAD CURRENT
(ADJUSTABLE MODE)
V
IN
= 6.5V
90
EFFICIENCY (%)
V
IN
= 8V
V
IN
= 12V
70
V
IN
= 18V
V
IN
= 24V
V
OUT
= 5.0V
MAX1864/65 toc03
100
V
IN
= 6.5V
90
EFFICIENCY (%)
3.33
3.32
OUTPUT VOLTAGE (V)
3.31
3.30
3.29
3.28
100
80
V
IN
= 8V
70
V
IN
= 12V
V
IN
= 18V
60
V
IN
= 24V
V
OUT
= 3.3V
50
0.01
0.1
1
10
LOAD CURRENT (A)
80
60
3.27
0
0.5
1.0
1.5
2.0
2.5
3.0
LOAD CURRENT (A)
50
0.01
0.1
1
10
LOAD CURRENT (A)
_______________________________________________________________________________________
5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
